What was found
AFTER 10 MIN AT 37,000 FT CABIN ALTITUDE BEGAN CLIMBING TO 10,000 FT. DIFFERENTIAL PRESSURE STAYED AT 7.2, NO CHANGE IN ALTN MODE. BEGAN DESCENT AND CABIN PRESSURE DECREASED TO NORMAL RANGE. OUTFLOW VALVE SHOWED CLOSED ENTIRE SEQUENCE. REMOVED AND REPLACED CABIN PRESSURIZATION OUTFLOW VALVE (AFT) PER M/M, OPS CHECKS GOOD PER MM.